Client Single Login and duplicate connects

I’ve tried searching this forum and can not find anything about Client Single Login and duplicate connections.

I’m seeing on my Domino Server under Server → Notes Users - duplicate connections for almost every Notes user. A connection to their mail file and then a second line - a blank connection line (using the same IP) but a different port number. We are using Client Single Login and I was wondering if that is the “blank” connection. I don’t use Client Single Login and I only see my one connection.

Thank you in advance !